You wouldn't know it from the deep snowpack covering the park, but some of Yellowstone's bears may be thinking that winter 2011 is drawing to a close.

On Tuesday, March 1, park employees observed grizzly bear tracks on Mary Mountain, which is roughly near the center of the lower loop of the park's Grand Loop Road. Bears begin looking for food soon after they emerge from their dens, park rangers said. They are attracted to elk and bison which have died during the winter. Carcasses are an important enough food source that bears will sometimes react aggressively when surprised while feeding on them.

Park regulations require visitors to stay 100 yards from black and grizzly bears at all times. The best defense is to stay a safe distance from bears and use binoculars, a telescope, or a camera's telephoto lens to get a closer look.

Hikers, snowshoers, and cross-country skiers are encouraged to travel in groups of three or more, make noise on the trail, and keep an eye out for bears, ranger said. Bear pepper spray has proven to be a good last line of defense, if kept handy and used according to directions when the bear is within 30 to 40 feet, they added.

While firearms are allowed in the park, the discharge of a firearm is a violation of park regulations. Even the park's law enforcement rangers who carry firearms on duty rely on pepper spray, rather than their weapons, as the most effective means to deal with a bear encounter.

Seasonal Bear Management Area closures are designed to reduce encounters with bears in areas that have a high density of elk and bison carcasses, and provide areas where bears can roam free from human disturbance.

Prior to hiking, skiing, or snowshoeing in the park, visitors are encouraged to check the park web site at www.nps.gov/yell/parkmgmt/bearclosures.htm or at park visitor centers for dates and locations of bear closure areas.

Visitors are also reminded to keep food, garbage, barbecue grills and other attractants stored in hard-sided vehicles or bear-proof food storage boxes, rangers said. This helps keep bears from becoming conditioned to human foods, and helps keep park visitors and their property safe.

Bear sightings should be reported to the nearest visitor center or ranger station as soon as possible, they added.